/*! 
FastSqrt for the EpLibrary

The MIT License (MIT)

Copyright (c) 2008-2013 Woong Gyu La <juhgiyo@gmail.com>

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.

------------------------------------------------------------------------------

Part of this software is

Anti-Grain Geometry - Version 2.4
Copyright (C) 2002-2005 Maxim Shemanarev (http://www.antigrain.com)

Permission to copy, use, modify, sell and distribute this software 
is granted provided this copyright notice appears in all copies. 
This software is provided "as is" without express or implied
warranty, and with no claim as to its suitability for any purpose.

----------------------------------------------------------------------
Contact: mcseem@antigrain.com
mcseemagg@yahoo.com
http://www.antigrain.com
----------------------------------------------------------------------
Bessel function (besj) was adapted for use in AGG library by Andy Wilk 
Contact: castor.vulgaris@gmail.com

----------------------------------------------------------------------

*/

#include "epFastSqrt.h"

#if defined(_DEBUG) && defined(EP_ENABLE_CRTDBG)
#define new DEBUG_NEW
#undef THIS_FILE
static char THIS_FILE[] = __FILE__;
#endif // defined(_DEBUG) && defined(EP_ENABLE_CRTDBG)

using namespace epl;

const unsigned short g_sqrt_table[1024] = 
{
	0,
	2048,2896,3547,4096,4579,5017,5418,5793,6144,6476,6792,7094,7384,7663,7932,8192,8444,
	8689,8927,9159,9385,9606,9822,10033,10240,10443,10642,10837,11029,11217,11403,11585,
	11765,11942,12116,12288,12457,12625,12790,12953,13114,13273,13430,13585,13738,13890,
	14040,14189,14336,14482,14626,14768,14910,15050,15188,15326,15462,15597,15731,15864,
	15995,16126,16255,16384,16512,16638,16764,16888,17012,17135,17257,17378,17498,17618,
	17736,17854,17971,18087,18203,18318,18432,18545,18658,18770,18882,18992,19102,19212,
	19321,19429,19537,19644,19750,19856,19961,20066,20170,20274,20377,20480,20582,20684,
	20785,20886,20986,21085,21185,21283,21382,21480,21577,21674,21771,21867,21962,22058,
	22153,22247,22341,22435,22528,22621,22713,22806,22897,22989,23080,23170,23261,23351,
	23440,23530,23619,23707,23796,23884,23971,24059,24146,24232,24319,24405,24491,24576,
	24661,24746,24831,24915,24999,25083,25166,25249,25332,25415,25497,25580,25661,25743,
	25824,25905,25986,26067,26147,26227,26307,26387,26466,26545,26624,26703,26781,26859,
	26937,27015,27092,27170,27247,27324,27400,27477,27553,27629,27705,27780,27856,27931,
	28006,28081,28155,28230,28304,28378,28452,28525,28599,28672,28745,28818,28891,28963,
	29035,29108,29180,29251,29323,29394,29466,29537,29608,29678,29749,29819,29890,29960,
	30030,30099,30169,30238,30308,30377,30446,30515,30583,30652,30720,30788,30856,30924,
	30992,31059,31127,31194,31261,31328,31395,31462,31529,31595,31661,31727,31794,31859,
	31925,31991,32056,32122,32187,32252,32317,32382,32446,32511,32575,32640,32704,32768,
	32832,32896,32959,33023,33086,33150,33213,33276,33339,33402,33465,33527,33590,33652,
	33714,33776,33839,33900,33962,34024,34086,34147,34208,34270,34331,34392,34453,34514,
	34574,34635,34695,34756,34816,34876,34936,34996,35056,35116,35176,35235,35295,35354,
	35413,35472,35531,35590,35649,35708,35767,35825,35884,35942,36001,36059,36117,36175,
	36233,36291,36348,36406,36464,36521,36578,36636,36693,36750,36807,36864,36921,36978,
	37034,37091,37147,37204,37260,37316,37372,37429,37485,37540,37596,37652,37708,37763,
	37819,37874,37929,37985,38040,38095,38150,38205,38260,38315,38369,38424,38478,38533,
	38587,38642,38696,38750,38804,38858,38912,38966,39020,39073,39127,39181,39234,39287,
	39341,39394,39447,39500,39553,39606,39659,39712,39765,39818,39870,39923,39975,40028,
	40080,40132,40185,40237,40289,40341,40393,40445,40497,40548,40600,40652,40703,40755,
	40806,40857,40909,40960,41011,41062,41113,41164,41215,41266,41317,41368,41418,41469,
	41519,41570,41620,41671,41721,41771,41821,41871,41922,41972,42021,42071,42121,42171,
	42221,42270,42320,42369,42419,42468,42518,42567,42616,42665,42714,42763,42813,42861,
	42910,42959,43008,43057,43105,43154,43203,43251,43300,43348,43396,43445,43493,43541,
	43589,43637,43685,43733,43781,43829,43877,43925,43972,44020,44068,44115,44163,44210,
	44258,44305,44352,44400,44447,44494,44541,44588,44635,44682,44729,44776,44823,44869,
	44916,44963,45009,45056,45103,45149,45195,45242,45288,45334,45381,45427,45473,45519,
	45565,45611,45657,45703,45749,45795,45840,45886,45932,45977,46023,46069,46114,46160,
	46205,46250,46296,46341,46386,46431,46477,46522,46567,46612,46657,46702,46746,46791,
	46836,46881,46926,46970,47015,47059,47104,47149,47193,47237,47282,47326,47370,47415,
	47459,47503,47547,47591,47635,47679,47723,47767,47811,47855,47899,47942,47986,48030,
	48074,48117,48161,48204,48248,48291,48335,48378,48421,48465,48508,48551,48594,48637,
	48680,48723,48766,48809,48852,48895,48938,48981,49024,49067,49109,49152,49195,49237,
	49280,49322,49365,49407,49450,49492,49535,49577,49619,49661,49704,49746,49788,49830,
	49872,49914,49956,49998,50040,50082,50124,50166,50207,50249,50291,50332,50374,50416,
	50457,50499,50540,50582,50623,50665,50706,50747,50789,50830,50871,50912,50954,50995,
	51036,51077,51118,51159,51200,51241,51282,51323,51364,51404,51445,51486,51527,51567,
	51608,51649,51689,51730,51770,51811,51851,51892,51932,51972,52013,52053,52093,52134,
	52174,52214,52254,52294,52334,52374,52414,52454,52494,52534,52574,52614,52654,52694,
	52734,52773,52813,52853,52892,52932,52972,53011,53051,53090,53130,53169,53209,53248,
	53287,53327,53366,53405,53445,53484,53523,53562,53601,53640,53679,53719,53758,53797,
	53836,53874,53913,53952,53991,54030,54069,54108,54146,54185,54224,54262,54301,54340,
	54378,54417,54455,54494,54532,54571,54609,54647,54686,54724,54762,54801,54839,54877,
	54915,54954,54992,55030,55068,55106,55144,55182,55220,55258,55296,55334,55372,55410,
	55447,55485,55523,55561,55599,55636,55674,55712,55749,55787,55824,55862,55900,55937,
	55975,56012,56049,56087,56124,56162,56199,56236,56273,56311,56348,56385,56422,56459,
	56497,56534,56571,56608,56645,56682,56719,56756,56793,56830,56867,56903,56940,56977,
	57014,57051,57087,57124,57161,57198,57234,57271,57307,57344,57381,57417,57454,57490,
	57527,57563,57599,57636,57672,57709,57745,57781,57817,57854,57890,57926,57962,57999,
	58035,58071,58107,58143,58179,58215,58251,58287,58323,58359,58395,58431,58467,58503,
	58538,58574,58610,58646,58682,58717,58753,58789,58824,58860,58896,58931,58967,59002,
	59038,59073,59109,59144,59180,59215,59251,59286,59321,59357,59392,59427,59463,59498,
	59533,59568,59603,59639,59674,59709,59744,59779,59814,59849,59884,59919,59954,59989,
	60024,60059,60094,60129,60164,60199,60233,60268,60303,60338,60373,60407,60442,60477,
	60511,60546,60581,60615,60650,60684,60719,60753,60788,60822,60857,60891,60926,60960,
	60995,61029,61063,61098,61132,61166,61201,61235,61269,61303,61338,61372,61406,61440,
	61474,61508,61542,61576,61610,61644,61678,61712,61746,61780,61814,61848,61882,61916,
	61950,61984,62018,62051,62085,62119,62153,62186,62220,62254,62287,62321,62355,62388,
	62422,62456,62489,62523,62556,62590,62623,62657,62690,62724,62757,62790,62824,62857,
	62891,62924,62957,62991,63024,63057,63090,63124,63157,63190,63223,63256,63289,63323,
	63356,63389,63422,63455,63488,63521,63554,63587,63620,63653,63686,63719,63752,63785,
	63817,63850,63883,63916,63949,63982,64014,64047,64080,64113,64145,64178,64211,64243,
	64276,64309,64341,64374,64406,64439,64471,64504,64536,64569,64601,64634,64666,64699,
	64731,64763,64796,64828,64861,64893,64925,64957,64990,65022,65054,65086,65119,65151,
	65183,65215,65247,65279,65312,65344,65376,65408,65440,65472,65504
};


const char g_elder_bit_table[256] = 
{
	0,0,1,1,2,2,2,2,3,3,3,3,3,3,3,3,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,
	5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,
	6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,
	6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,
	7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
	7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
	7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
	7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7
};

unsigned int FastSqrt::Sqrt(const unsigned int val)
{
	//This code is actually pure C and portable to most 
	//arcitectures including 64bit ones. 
	unsigned int t = val;
	int bit=0;
	unsigned int shift = 11;

	//The following piece of code is just an emulation of the
	//Ix86 assembler command "bsr" (see above). However on old
	//Intels (like Intel MMX 233MHz) this code is about twice 
	//faster (sic!) then just one "bsr". On PIII and PIV the
	//bsr is optimized quite well.
	bit = t >> 24;
	if(bit)
	{
		bit = g_elder_bit_table[bit] + 24;
	}
	else
	{
		bit = (t >> 16) & 0xFF;
		if(bit)
		{
			bit = g_elder_bit_table[bit] + 16;
		}
		else
		{
			bit = (t >> 8) & 0xFF;
			if(bit)
			{
				bit = g_elder_bit_table[bit] + 8;
			}
			else
			{
				bit = g_elder_bit_table[t];
			}
		}
	}

	//This is calculation sqrt itself.
	bit -= 9;
	if(bit > 0)
	{
		bit = (bit >> 1) + (bit & 1);
		shift -= bit;
		//val >>= (bit << 1);
		t >>= (bit << 1);
	}
	//return g_sqrt_table[val] >> shift;
	return g_sqrt_table[t] >> shift;
}


